EP4072701A1

EP4072701A1 - Method for regenerating an aqueous solution of meg containing salts with purge treatment

Info

Publication number: EP4072701A1
Application number: EP20816470.7A
Authority: EP
Inventors: Bruno Delfort; Aurélie WENDER; Elsa Muller; Xavier COURTIAL; Guillaume PARER; Pierre-Yves LANFREY
Original assignee: IFP Energies Nouvelles IFPEN; Axens SA
Current assignee: IFP Energies Nouvelles IFPEN; Axens SA
Priority date: 2019-12-13
Filing date: 2020-12-01
Publication date: 2022-10-19
Anticipated expiration: 2040-12-01
Also published as: AU2020399117A1; FR3104452B1; EP4072701B1; FR3104452A1; WO2021115852A1; US20230023829A1; BR112022007360A2

Abstract

The present invention relates to a method for regenerating a MEG-rich aqueous solution (100), recovering a maximum amount of MEG whilst eliminating the salts of carboxylic acids, comprising: a) vacuum vaporisation of the solution (100) in a unit (1000); b) optional precipitation in a tank (1002) of the inorganic salts of a portion (105) of the liquid residue enriched with MEG and with salts (104) originating from a); c) elimination of the precipitated inorganic salts in a solid/liquid separation unit (1003); d) sending all or some (114) of the liquid effluent (112) originating from c) to a separation unit (1004) different from the unit (1000) in order to particularly form a flow of MEG depleted of carboxylic acid salts or carboxylic acids (115); e) recycling said flow (115) to step a).

Description

REGENERATION PROCESS OF AN AQUEOUS MEG SOLUTION CONTAINING SALTS

WITH PURGE TREATMENT

Technical area

The present invention relates to the field of the regeneration of an aqueous solution of monoethylene glycol (MEG) containing dissolved salts used for the transport of natural gas.

Prior art

Natural gas leaving production wells is often associated with reservoir water containing dissolved salts (sodium chloride, potassium chloride, calcium chloride, sodium bicarbonate, etc.). Natural gas is transported from the place of production to a place of treatment by circulation in pipes. Depending on the transport conditions, and in particular the pressure and the temperature, it is possible that the water contained in the natural gas forms hydrate plugs which can lead to production being stopped.

To avoid these problems, a hydrate inhibitor is usually injected into the transport lines. MEG, also called ethane-1,2-diol or ethylene glycol, is commonly used as a hydrate inhibitor in the transport of natural gas, often saturated with water, from the place of production to the place of processing. The MEG is conventionally injected at the level of the drilling wells to secure the transport of natural gas to the processing units. To do this, an aqueous solution containing between 70% and 95% by weight of MEG, known under the name of purified MEG or “Lean MEG” in English, is used.

Once separated from the condensates and the natural gas, the aqueous phase recovered forms a solution generally containing between 15% and 60% by weight of MEG, called “Rich MEG” in English or “rich MEG” solution. The rich MEG solution is composed of the purified MEG injected at the top of the well, water from the underground formation and salts originating from this formation, water resulting from the condensation of the gas and traces of dissolved and free hydrocarbons. The rich MEG solution thus needs to be regenerated and desalted in order to be able to be reused for its injection at the top of the wellbore. The process allowing regeneration and desalting is generally called by the generic term "MEG reclaiming".

MEG enters the reclaiming process with impurities such as for example water, hydrocarbons, inorganic salts such as for example sodium chloride or potassium chloride, and salts derived from carboxylic acids such for example sodium and potassium formates, acetates, propionates, butyrates, oxalates and glycolates. At the end of the process, the MEG has been regenerated / desalted and is in the form of a MEG / water mixture that can be reinjected at the borehole head, which is the aqueous solution comprising between 70% and 95% by weight of MEG known as Purified MEG ("Lean MEG"), also referred to in the present description as a regenerated MEG solution.

MEG distillation systems for separating the MEG from the water and MEG mixture are known to those skilled in the art, these methods being referred to as MEG regeneration methods. In general, the systems of the prior art make it possible to obtain an aqueous solution containing between 70% and 95% by weight of MEG.

Moreover, if the salts are not removed from the rich MEG solution, the regeneration of the MEG leads to the concentration and accumulation of the salts, mainly coming from the water of the underground formation, in the regenerated MEG solution and in the loops. from the regeneration process. The accumulation of these salts is at the origin of many operating problems, such as, for example, clogging phenomena of the MEG regeneration installations which can go as far as causing them to stop. This is the reason why the MEG regeneration processes can comprise, in addition to the separation of the water from the MEG, a step of desalting the MEG, in particular in processes operating at pressures below atmospheric pressure.

The rich MEG solution, containing water and dissolved salts, thus comprises:

- salts which precipitate under conditions compatible with regeneration and desalting installations for rich MEG solutions, such as inorganic salts such as sodium chloride, potassium chloride, calcium chloride, sodium bicarbonate, etc. ;

- salts which do not precipitate under conditions compatible with regeneration and desalting installations for rich MEG solutions, such as organic salts, such as salts of formate-type carboxylic acids, acetate, propionate, butyrate , etc., from natural gas and / or water from the underground formation, and / or degradation of MEG.

The salts of carboxylic acids are extremely soluble in aqueous MEG solutions, and do not precipitate at low concentration, unlike inorganic salts. They can also be present in the aqueous MEG solution in the form of carboxylic acids, which are volatile, depending on the pH of the aqueous MEG solution considered. On the contrary, in the form of salts, in particular of alkali, alkaline earth or metallic salts, the salts of organic acids are not volatile.

Currently, most of the regeneration and desalting processes of rich MEG solutions make it possible to remove a large part of the water by distillation and inorganic salts by precipitation.

On the other hand, the elimination of salts of carboxylic acids remains problematic.

The salts of organic acids, in particular the salts of carboxylic acids, once solubilized, tend to accumulate in the MEG solutions, in particular at the level of the recycle loops of the vaporization units of the regeneration and desalting installations. The more solubilized / accumulated organic salts there are in the MEG solution, the more the viscosity of the solution increases. In this, when they accumulate in the process, the salts of solubilized organic acids can cause phenomena of MEG freezing and thus lead to operational problems, or even to the shutdown of the unit. The energy required for regeneration is also likely to increase.

It is thus necessary to control the concentration of carboxylic acid salts dissolved in the MEG vaporization loops during the operation of the process in order to limit the increase in viscosity and to avoid the phenomena of clogging of the installations. It is known to those skilled in the art the possibility of controlling the salt content in the regeneration process by using a purge. Said purge allows part of the dissolved and / or suspended salts to be evacuated from the unit by purging a stream comprising dissolved and / or suspended salts as well as MEG. The quantity of purged salts is adapted to maintain the concentration of solubilized and / or suspended salts during operation and therefore to avoid an increase in viscosity which could cause the phenomena of clogging of the installations.

For example, patent EP1261410 describes an installation and a method for purifying hydrate formation inhibitors such as MEG. The management of the salts dissolved in the MEG solution is carried out by means of a purge: the MEG to be treated is sent to a flash flask or a column operating under vacuum so as to separate a liquid stream at the bottom of the flask (or column) comprising MEG and the salts, and at the top of the flask (or column) an essentially gaseous flow comprising water and MEG. The flow of MEG and salts is partly reheated to be recycled to the flask (or column), the other part is purged, the purged quantity depending on the salt concentration. This purge makes it possible to prevent the saturation and precipitation of salts in the liquid flow of MEG and salts at the outlet of the flask (or column). The head stream is vacuum distilled to separate the water and the gases (at the head) and recover the purified MEG (at the bottom) which is recycled to the natural gas field. US5993608 also discloses the possibility of performing a similar purge on the liquid effluent from a vapor / liquid separation zone receiving the MEG solution.

However, such a purge results in a loss of MEG, which reduces the efficiency of the regeneration process.

The present invention relates to a process aimed at limiting the loss of MEG encountered during traditional purges carried out to remove organic acid salts from the system, and aimed at limiting the accumulation of these salts in the installation.

Certain MEG purification methods are known which take into account the problem of the accumulation of organic acid salts in the MEG solution.

Thus, US Pat. No. 92,84,244 describes a method of precipitation and elimination of carboxylic acid salts from a MEG solution which consists in forcing the precipitation of these salts by adding an antisolvent and also by adding a solution of inorganic salts comprising divalent cations. In this document it is described that the performance is achieved due to the introduction of chemical compounds.

US9732019 describes a method for stripping certain carboxylic acids from a rich MEG solution, by bringing the rich MEG solution into contact with a stripping gas in a stripping column. This method concerns carboxylic acids and not their salts. According to this method, the entire flow of rich MEG solution to be regenerated is subjected to stripping.

Objectives and Summary of the Invention

The general objective of the present invention is to provide a process for the regeneration and desalting of a rich MEG solution making it possible to recover a maximum of MEG to form the regenerated solution while eliminating the inorganic salts and at least in part the acid salts. carboxylic acids present in the solution. The present invention thus aims in particular to avoid the harmful effects of an increase in the concentration of salts of carboxylic acids dissolved in the MEG solution during its regeneration, in particular a significant increase in viscosity which may lead to clogging phenomena. or other operational problems in the regeneration plant.

In particular, the present invention aims to fulfill at least one of the following objectives:

- eliminating at least in part, preferably completely, the carboxylic acid salts from the aqueous MEG solution during the steps of the regeneration process while maximizing the amount of MEG recovered serving to form the regenerated MEG solution;

- remove the carboxylic acid salts from the aqueous MEG solution during the stages of the regeneration process while maximizing the amount of MEG recovered serving to form the regenerated MEG solution, without resorting to the addition of compounds or reagents chemicals that promote the precipitation of carboxylic acid salts.

It was thus demonstrated by the inventors that it was possible to achieve at least one of these objectives by treating the rich MEG aqueous solution by a regeneration and desalting process comprising a series of operations, in particular operations adapted to the removal of each type of salts, ie inorganic salts and salts of carboxylic acids, to provide a regenerated MEG solution.

Thus, to achieve at least one of the aforementioned objectives, among others, the present invention proposes, according to a first aspect, a process for regenerating a MEG solution containing water and dissolved salts, comprising the following steps: a) said solution is vaporized under vacuum in a first vaporization unit to produce a gaseous effluent comprising MEG and water, and a liquid residue enriched in MEG and in salts, a first part of which is recycled into said first vacuum vaporization unit; b) optionally, a second part of said liquid residue enriched in MEG and salts is sent into a tank in which the temperature of said second part of said liquid residue enriched in salts is lowered so as to precipitate inorganic salts to form a flow enriched in salts precipitates, a first fraction of which is preferably recycled to the tank and a flow depleted in precipitated salts recycled to the vacuum vaporization unit in step a); c) is sent, preferably intermittently, said second part of said liquid residue enriched in MEG and salts from step a) or a second fraction of said stream enriched in precipitated salts obtained in step b), in a solid / liquid separation zone for separating a stream containing precipitated salts comprising inorganic salts and a liquid effluent comprising dissolved salts among which salts of carboxylic acids; d) is sent, preferably intermittently, a portion or all of said liquid effluent obtained in step c) in a separation unit different from the first vacuum vaporization unit to operate a separation between the MEG and at least in part the salts of carboxylic acids or carboxylic acids capable of producing said salts of carboxylic acids and forming a flow of MEG depleted in salts of carboxylic acids in carboxylic acids and a residual flow enriched in salts of carboxylic acids or in carboxylic acids; e) said flow of MEG depleted in salts of carboxylic acids or in carboxylic acids in step a) is recycled, or said flow of MEG depleted in salts of carboxylic acids or in carboxylic acids is mixed with the gaseous effluent comprising MEG and water from step a), and said gaseous effluent comprising MEG and water from step a) or said mixture is used to produce the regenerated MEG solution.

According to one or more implementations, in step e) the flow of MEG depleted in carboxylic acid salts or in carboxylic acids resulting from step d) is recycled to step a).

A step f) of purification of the gaseous effluent from step a) can also be carried out in a purification unit to form a stream of water and the regenerated MEG solution, preferably comprising from 70% to 95%. % by weight of MEG.

This purification step f) can be vacuum distillation, preferably carried out at a pressure of between 0.01 MPa and 0.07 MPa.

According to one or more implementations, prior to step a), vaporization is carried out at atmospheric pressure of the MEG solution containing water and dissolved salts to be regenerated in an initial vaporization unit, preferably at an atmospheric pressure. temperature between 100 ° C and 155 ° C and a pressure between 0.1 MPa and 0.15 MPa, to produce a gaseous effluent enriched in water and a liquid residue enriched in MEG and salts, all of which is sent to the 'step a).

According to one or more implementations, step a) is carried out at a temperature between 120 ° C and 155 ° C, and a pressure between 0.01 MPa and 0.07 MPa.

According to one or more implementations, step c) is carried out at a temperature between 50 ° C and 90 ° C and at atmospheric pressure, preferably at a pressure between 0.1 MPa and 0.15 MPa.

According to one or more implementations, the second fraction of said stream enriched in precipitated salts from the reservoir is sent to the solid / liquid separation unit intermittently, preferably if the concentration of inorganic salts of said stream enriched in precipitated salts is between 10% by weight and 50% by weight, preferably between 15% by weight and 30% by weight.

According to one or more implementations, the portion or all of said liquid effluent obtained in step c) is sent intermittently to the separation unit of step d).

According to one or more implementations, in step d) the separation unit is chosen from a second vaporization unit or a liquid / liquid extraction unit or a membrane separation unit or a separation unit by acidification and stripping.

According to one or more implementations, in step d) the separation unit is a second vaporization unit, and the portion or all of said liquid effluent obtained in step c) is vaporized under vacuum to form a vapor enriched in MEG and depleted in carboxylic acid salts and a residual liquid effluent enriched in carboxylic acid salts.

An additional liquid or gaseous stream can be sent into said second vaporization unit to increase the quantity of MEG recovered in the stream during step d), said stream being chosen from water, water vapor, or a inert gas. Advantageously, said step d) is carried out at a temperature of between 120 ° C and 155 ° C, and a pressure of between 0.01 MPa and 0.07 MPa.

According to one or more implementations, in step d) the separation unit is a liquid / liquid extraction unit, and the portion of said liquid effluent obtained in step c) is brought into contact with a liquid d 'extraction, preferably at a temperature between 50 ° C and 100 ° C and a pressure between 0.1 MPa and 0.15 MPa, to form a liquid flow of MEG depleted in salts of carboxylic acids and a residual flow liquid enriched with carboxylic acid salts comprising the majority of the extraction liquid.

According to one or more implementations, in step d) the separation unit is a membrane separation unit, and the portion of said liquid effluent obtained in step c) is brought into contact with one or more membranes, preferably at a temperature between 50 ° C and 100 ° C and a pressure between 0.1 MPa and 0.15 MPa, to form a liquid flow of MEG depleted in salts of carboxylic acids and a residual liquid flow enriched in salts of carboxylic acids.

According to one or more implementations, the separation unit is a unit for separation by acidification and stripping, and the portion of said liquid effluent obtained in step c) is acidified and then said acidified liquid effluent is stripped with a stripping gas. , preferably nitrogen, preferably at a temperature between 50 ° C and 100 ° C and a pressure between 0.1 MPa and 0.15 MPa, to form a liquid flow of MEG depleted in carboxylic acids and a gaseous residual flow enriched in carboxylic acids.

Other objects and advantages of the invention will become apparent on reading the following description of examples of particular embodiments of the invention, given by way of nonlimiting examples, the description being given with reference to the appended figures described below. -after.

List of Figures

FIG. 1 represents a diagram of the process for regenerating an MEG solution according to one embodiment of the invention.

FIG. 2 represents a diagram of the process for regenerating an MEG solution according to another embodiment of the invention.

In the figures, the same references designate identical or similar elements.

Description of the embodiments

Two embodiments of the method according to the invention are illustrated in FIGS. 1 and 2, and serve for the following description of the method for a better understanding of the steps and of the various flows involved.

These illustrations of the process according to the invention do not include all of the components necessary for its implementation, for example heat exchangers, pumps, mixers, etc. Only the elements necessary for understanding the invention are represented therein, a person skilled in the art being able to complete these representations in order to implement the invention. The expression "between ... and ..." means that the limit values of the interval are included in the range of values described, unless specified otherwise.

Throughout the description, the sum of the mass fractions expressed as% by weight of the various compounds of a solution is equal to 100% by weight of said solution.

The mass fractions of MEG and water of a stream / effluent are expressed in% by weight of the stream / effluent excluding salts, i.e. not taking salts into account, unless otherwise specified.

In the present description, the steps are operated continuously, unless their intermittent operation is specified.

In the present description, the pressures are expressed in absolute values, unless indicated otherwise.

In the present invention, the different parameter ranges for a given step such as pressure ranges and temperature ranges can be used alone or in combination. For example, in the present invention, a preferred range of pressure values may be combined with a more preferred range of temperature values.

In the present description, the terms “enriched” and “depleted” in one or more compounds in an effluent / outgoing flow at a stage must be understood in relation to the concentration of said compound (s) in an effluent / incoming flow. . Thus an outgoing flow enriched in MEG means that the outgoing flow has a higher MEG concentration than the MEG concentration of the incoming flow. Likewise, an outgoing flow depleted in salts contains a lower salt concentration than the salt concentration of the incoming flow.

According to the invention, the process for regenerating an MEG solution containing water and dissolved salts comprises, and may consist of, the following steps, preferably in this order: a) vaporization of the solution under vacuum of MEG containing water and dissolved salts 100 in a first vacuum vaporization unit 1000. This vacuum vaporization makes it possible to produce a gaseous effluent comprising MEG and water 101, and a liquid residue enriched in MEG and in salts 104. A first part 106 of the liquid residue enriched in MEG and in salts 104 is recycled into the first vacuum vaporization unit 1000. b) Preferably, and as illustrated in FIG. 2, a second is sent. part 105 of the liquid residue enriched in MEG and in salts 104 resulting from step a) in a reservoir 1002, in which the temperature of the flow 105 is lowered so as to precipitate inorganic salts. A stream enriched in precipitated salts 108 is then formed, a fraction 109 of which is preferably recycled into the reservoir 1002, and a stream depleted in precipitated salts 107 recycled into the vacuum vaporization unit 1000 in step a). c) Is sent, preferably intermittently, a second part 105 of said liquid residue enriched in MEG and salts 104 from step a) as illustrated in Figure 1 (case without step b)), or at least a fraction 110 of said stream enriched in precipitated salts 108 obtained in step b) as illustrated in FIG. 2, in a solid / liquid separation zone 1003 to separate a stream containing salts precipitates comprising inorganic salts 111 and a liquid effluent comprising dissolved salts among which salts of carboxylic acids 112. d) Is sent, preferably intermittently, a portion 114 of the liquid effluent 112 obtained in step c ) in a separation unit 1004 different from the first vacuum vaporization unit 1000, to perform a separation between the MEG and at least in part the salts of carboxylic acids or carboxylic acids capable of producing said salts of carboxylic acids of the MEG. A flow of MEG is then formed which is depleted in salts of carboxylic acids or in carboxylic acids 115 and a residual flow enriched in salts of carboxylic acids or in carboxylic acids 116. e) The flow of MEG depleted in acid salts is recycled. carboxylic acid or carboxylic acid 115 in step a) or mixing the flow of MEG depleted in carboxylic acid salts or carboxylic acids 115 and the gaseous effluent comprising MEG and water 101 from step a), and said gaseous effluent comprising MEG and water 101 from step a) or said mixture is used to produce the regenerated MEG solution.

Advantageously, the regeneration process according to the invention further comprises one or more

- a step of purification of the rich MEG solution 100, containing water and dissolved salts, prior to step a), in particular vaporization at substantially atmospheric pressure, to form a stream of water (gaseous effluent enriched in water) and an aqueous MEG solution depleted in water and containing salts, sent in full to step a) (not shown in the figures);

- and / or a step f) of purification of the gaseous effluent 101 resulting from step a) in a purification unit 1001 to form a stream of water 103 and a regenerated solution of MEG 102, preferably comprising 70 % to 95% by weight of MEG.

Step f) is preferably vacuum distillation, advantageously carried out at a pressure of between 0.01 MPa and 0.07 MPa.

Rich MEG solution 100 to regenerate

The aqueous solution of MEG 100 to be regenerated contains dissolved salts, potentially up to several molar percent, which include inorganic salts, such as sodium chloride, potassium chloride, calcium chloride, sodium bicarbonate, etc., but which can also comprise organic salts, such as salts of carboxylic acids, for example of formate type (HCOO), acetate (CH ₃ COO), propionate (C ₂ H ₅ COO), butyrate (C ₃ H ₇ COO), etc.

The carboxylic acid salts are generally present in the aqueous solution of MEG 100 to be regenerated, which enters the first vacuum vaporization unit 1000 in step a), and can come from natural gas and / or from water. training. Thus the process according to the invention aims in particular to eliminate at least in part, and preferably in full, the salts of carboxylic acids present in the rich MEG solution sent to the vacuum vaporization step a), and which s 'accumulate during the regeneration process. In the present description, the aqueous MEG 100 solution to be regenerated which contains dissolved salts is also referred to as “rich” MEG solution.

The rich MEG 100 solution generally contains between 20% by weight and 50% by weight of MEG. The remainder of the solution is water, except for impurities.

The rich MEG solution can also contain other impurities, generally in small quantities, from a few tens of ppm molars to a few molar percentages, for example hydrocarbons resulting in particular from underground formations, dissolved gases such as C0 ₂ , del ' H ₂ S.

The inorganic salts can precipitate under the operating conditions of certain steps of the process, in particular in vaporization step a), but also in particular in step b) when this step is carried out. They are separated from the rest of the water and MEG solution in step c) of solid / liquid separation, and discharged out of the process and of the regeneration installation.

The carboxylic acid salts, which for the most part do not precipitate under the operating conditions of the process steps, are mainly separated from the rest of the water and MEG solution and are discharged out of the process and the installation to step d) of separation.

The pH of the MEG 100 solution to be regenerated is preferably between 7 and 14, typically of the order of 10.5 to 11. Such a pH can be obtained by adjusting the pH, for example by adding sodium hydroxide to the mixture. rich MEG solution before it is sent to the vacuum vaporization unit 1000 in step a).

Such a pH prevents the carboxylic acid salts from being in the form of carboxylic acids, and prevents them from being vaporized with water and MEG during vaporization step a).

The different steps of the process according to the invention are detailed below.

Vacuum vaporization step a)

During this step a), the rich MEG solution 100 is sent to the vacuum vaporization unit 1000 to be partially vaporized there.

The vacuum vaporization unit 1000 can be any vaporization device that can be operated under vacuum known to those skilled in the art, for example a balloon, also sometimes called an expansion balloon (or "flash" in English), due to vaporization produced by the vacuum operated in the flask and / or in the presence of a heating system. It can also be a vacuum distillation column.

This vacuum vaporization produces a gaseous effluent comprising, and preferably consisting of, MEG and water 101, and a liquid residue enriched in MEG and in salts 104. In fact, the vaporization makes it possible to separate an MEG / water mixture. essentially comprising the gaseous effluent 101, the rest of the rich MEG solution 100 entering the unit 1000, optionally mixed with one or more recycle streams (107, 113, 115) of the process described below. Due to the vaporization, the salts, whether inorganic or organic, are concentrated in the liquid phase very rich in MEG (typically comprising between 50% by weight and 99% by weight of MEG, preferably between 70% by weight and 99% weight of MEG, for example between 85% by weight and 99% by weight of MEG) contained in the vacuum vaporization unit 1000, and extracted from the unit 1000 in the form of the liquid residue enriched in MEG and salts 104. The most volatile impurities (C0 ₂ and dissolved hydrocarbons) potentially present in the solution of rich MEG 100 are also evaporated in the gas effluent 101.

The gaseous effluent 101 preferably contains substantially the same proportions of MEG and water as the solution of MEG 100 to be regenerated entering the unit 1000, due to the recycle streams (107, 113, 115) in the unit. 1000. In particular, the gaseous effluent 101 preferably comprises between 20% by weight and 50% by weight of MEG if the solution of MEG 100 to be regenerated comprises between 20% by weight and 50% by weight of MEG. The complement to the MEG in the gas effluent 101 being water, except for impurities.

A first part 106 of the liquid residue enriched in MEG and in salts 104 is recycled to the first vacuum vaporization unit 1000.

The concentration of salts in the liquid residue 104 is preferably between 7% by weight and 30% by weight (of the liquid residue), all types of salts combined, and more preferably between 9% by weight and 12% by weight (of the liquid residue). .

The concentration of inorganic salts in the internal recycle loop formed by flow 106 is preferably between 5% by weight and 20% by weight, preferably between 9% by weight and 12% by weight. This concentration is preferably maintained in this range by the flow 105 from the unit 1000.

The concentration of organic salts is preferably less than 30% by weight of the liquid residue, more preferably less than 10% by weight of the liquid residue, even more preferably less than 3% by weight of the liquid residue, and even more preferably less than 1% weight of liquid residue.

A second part of the liquid residue enriched in MEG and in salts 104 is sent either directly to step c) of liquid / solid separation, as illustrated in FIG. 1, or to a step b) of concentration and precipitation of the salts under the shape of the flow 105 as shown in Figure 2.

The recycling of the first part 106 of the liquid residue enriched in MEG and in salts 104 in the unit 1000 creates a recirculation loop, also called internal recycle loop, which makes it possible in particular to control the level of salts in the liquid residue enriched in MEG and in salts 104 by sending a second part either to step c) (flow 105 of FIG. 1) or to step b) (flow 105 of FIG. 2).

Preferably, the second part 105 of the liquid residue enriched in MEG and in salts 104, sent either directly to step c) or to step b), constitutes between 3 and 30% by weight of the liquid residue enriched in MEG and in salts 104, and more generally between 8% by weight and 12% by weight of residue 104. For example, the second part 105 of the liquid residue enriched in MEG and in salts 104, sent to step b), represents 10% by weight of the liquid residue enriched with MEG and salts 104.

Step a) is preferably carried out at a temperature between 100 ° C and 155 ° C, and at a pressure between 0.01 MPa and 0.07 MPa.

The operating pressure in the unit 1000 can be obtained by means of a vacuum pump, typically placed downstream of the unit 1000, in the direction of the flow of effluents leaving the unit 1000, for example downstream of the unit. 'gaseous effluent 101, or downstream of the water flow 103 (water vapor) from a distillation column 1001 receiving the gaseous effluent comprising water and MEG 101 when such a column is used. The operating temperature can be obtained thanks to a supply of heat by the first part 106 of the liquid residue enriched in MEG and in salts 104 recycled in the unit 1000, which is previously passed through a heat exchanger (not shown) in order to be heated.

The gaseous effluent comprising MEG and water 101 is used to produce the regenerated MEG solution, either directly, in particular when a step of purification of the rich MEG solution prior to step a) is carried out ( ie atmospheric distillation stage), or indirectly, in particular after an additional purification stage f) of said gaseous effluent 101 described later, where it is sent, alone or mixed with the flow 115 resulting from stage d), and of preferably alone.

Step b) of precipitation of inorganic salts - optional

The method preferably operates with step b), as illustrated in Figure 2.

In step b), a second part 105 of the liquid residue enriched in MEG and in salts 104 from step a) is sent to a tank 1002, in which the temperature of the flow 105 is lowered so as to precipitate salts. inorganic.

Preferably, the sending of the second part 105 of the liquid residue enriched in MEG and in salts 104 in the reservoir 1002 is carried out continuously or intermittently, and preferably continuously.

This storage of a portion 105 of the liquid residue 104 in a reservoir 1002 and its drop in temperature causes and / or increases the precipitation of inorganic salts.

A stream enriched in precipitated salts 108 is then formed and a stream depleted in precipitated salts 107 recycled to the vacuum vaporization unit 1000 in step a).

A first fraction 109 of the stream enriched in precipitated salts 108 is preferably recycled to the reservoir 1002. A second fraction 110 of the stream enriched in precipitated salts 108, complementary to the first fraction 109, is sent to step c). The fraction sent to step c) depends on the solid / liquid separation system, and can be intermittent or continuous.

The second fraction 110 of the stream enriched in precipitated salts 108 sent to step c) can constitute up to the entire stream enriched in precipitated salts 108 for intermittent operation. However, when the solid / liquid separation system used in step c) operates with intermittent operation, for example a solid / liquid separation system of the filtration type by basket centrifuge, it can be estimated that less than 1% of the daily flow circulating 108 is sent to 1003.

The tank 1002 constitutes a “passive” liquid / solid separation zone, by settling: the salts precipitated in suspension accumulate in the bottom by gravity, while the liquid rises. It is the latter which will form the flow depleted in precipitated salts 107 recycled in the vacuum vaporization unit 1000 in step a). Preferably, the pressure in the reservoir 1002 is of the order of 0.1 MPa, for example between 0.05 MPa and 0.15 MPa, more preferably between 0.08 MPa and 0.13 MPa, and the temperature between 40 ° C and 155 ° C, preferably between 55 ° C and 70 ° C. A gradient of temperature, pressure, salt concentration can be established in the tank 1002.

Preferably, the second fraction 110 of the stream enriched in precipitated salts 108 is sent to the solid / liquid separation unit 1003 intermittently.

This intermittent dispatch is advantageously carried out if the concentration of inorganic salts of the stream enriched in precipitated salts 108 is between 10% by weight and 50% by weight, preferably between 15% by weight and 30% by weight.

The intermittent delivery of the fraction 110 into the solid / liquid separation unit can for example be triggered by means of the control of a parameter linked to the concentration of inorganic salts of the stream 108, for example the density. For example, a density threshold value corresponding to a minimum inorganic salt concentration value, for example 10%, or preferably 15%, or a range of density threshold values corresponding to the inorganic salt concentration ranges, is determined. mentioned above, and the sending of the fraction 110 to the unit 1003 is triggered when the density measured, for example by a hydrometer, is beyond this threshold value or within the range of threshold values.

Non-intermittent, ie continuous, operation for sending the second fraction 110 of the stream enriched in precipitated salts 108 in step c) is possible: the fraction 110 of the stream enriched in precipitated salts 108 can be sent continuously into the stream. liquid / solid separation unit 1003 in step c).

Step c) of liquid-solid separation for the elimination of precipitated inorganic salts

During this step c), the second part 105 of the liquid residue enriched in MEG and in salts 104 resulting from step a) is sent, preferably intermittently, when the process does not include step b) as illustrated in FIG. 1, in a solid / liquid separation zone 1003 to separate a stream containing precipitated salts comprising inorganic salts 111 and a liquid effluent further comprising dissolved salts among which salts of carboxylic acids 112.

Alternatively, when the process comprises step b) as illustrated in FIG. 2, the second fraction 110 of the stream enriched in precipitated salts 108 obtained in step b) is sent, preferably intermittently, to the separation zone solid / liquid 1003 to separate a stream containing precipitated salts comprising inorganic salts 111 and a liquid effluent further comprising dissolved salts among which salts of carboxylic acids 112.

This step allows the separation of the precipitated salts, mainly inorganic salts, from the rest of the liquid received in unit 1003. This solid / liquid separation is carried out by any means known to those skilled in the art, for example a filtration device or a centrifuge, and preferably a centrifuge.

The stream containing the precipitated salts 111 comprises a salt cake exclusively composed of inorganic salts, as well as a little MEG and water and dissolved salts (inorganic and organic at saturation). The concentration of inorganic salts of stream 111 is for example between 80% by weight and 100% by weight, preferably between 85% by weight and 98% by weight, and more preferably between 90% by weight and 95% by weight.

The liquid stream 112 exiting the solid / liquid separation unit 1003, e.g. a centrifuge, comprises MEG, water, inorganic salts dissolved to saturation, and salts of dissolved carboxylic acids.

A portion 114 or all of the liquid effluent 112 is sent to the separation step d) for the removal of the salts of carboxylic acids described later. If only a portion 114 of the liquid effluent 112 is sent to the separation step d), the other portion 113 of the liquid effluent 112 is again sent to the unit 1000 in the vaporization step a). under vacuum.

Preferably, step c) is carried out at a temperature of between 50 ° C and 90 ° C and at substantially atmospheric pressure. For example, the pressure is between 0.1 MPa and 0.15 MPa, preferably between 0.1 MPa and 0.12 MPa.

As already mentioned above, for FIG. 2, the sending of the second fraction 110 of the stream enriched in precipitated salts 108 into the liquid / solid separation unit 1003 is preferably carried out intermittently.

For the embodiment illustrated in FIG. 1, which does not include step b), intermittent sending of the second part 105 of the stream 104, coming from the vacuum vaporization unit 1000, into the separation unit solid liquid 1003 is also possible.

However, continuous operation is possible, in which the liquid / solid separation unit 1003 continuously receives a liquid flow from which the crystallized salts are separated from the rest of the liquid flow, whether this liquid flow is the first fraction 110 of the flow 108 arriving from there. the reservoir 1002 (case of the embodiment illustrated in FIG. 2) or the second part 105 of the liquid residue enriched in MEG and in salts 104 coming from the vacuum vaporization unit 1000 in step a) (case of the mode embodiment illustrated in Figure 1).

The choice of intermittent or continuous operation for sending the liquid stream into the solid-liquid separation unit 1003 may depend on the technology used for the solid-liquid separation, for example the type of filtration system or centrifuge used.

Step d) separation for the removal of salts of carboxylic acids or carboxylic acids

According to the invention, in step d), a portion 114 or all of the liquid effluent 112 obtained in step c) is sent to a separation unit 1004 different from the first vacuum vaporization unit 1000 for separating at least in part the salts of carboxylic acids, or the carboxylic acids capable of producing the said salts of carboxylic acids, from the MEG, and forming a flow of MEG depleted in salts of carboxylic acids or in carboxylic acids 115 and a flow residual enriched in carboxylic acid salts or in carboxylic acids 116. The separation unit 1004 is also different from the liquid / solid separation unit 1003 of step c). Indeed, it aims to separate different compounds. Preferably, the separation unit 1004 is physically distinct from the vacuum vaporization unit 1000 and from the liquid / solid separation unit 1003.

The implementation of step d) in the method according to the invention makes it possible to process a flow of MEG 114 or 112 at a reduced flow rate, compared to the flow 101, which makes it possible to reduce the size of the equipment.

In step d), by separation “at least in part” of the salts of carboxylic acids, or of the carboxylic acids capable of producing said salts, from MEG, is meant:

- either that only part of the total quantity of the carboxylic acid salts is separated from the MEG, all types of carboxylic acid salts taken together, it being understood that the whole is preferably separated ("at least"),

- or that a single subfamily of carboxylic acids capable of producing certain carboxylic salts is preferably separated from the MEG. The latter case depends on the performance of the separation techniques and applies in particular to the embodiment (s) where step d) is carried out by acidification of the MEG solution and stripping of the acidified solution as detailed below. .

Preferably, the sending of a portion 114 or all of the liquid effluent 112 obtained in step c) into the separation unit 1004 is carried out intermittently.

Preferably, all of the liquid effluent 112 obtained in step c) is sent intermittently to the separation unit 1004.

The liquid stream 112 which exits the solid / liquid separation unit 1003 comprises MEG, water, inorganic salts dissolved to saturation, and salts of dissolved carboxylic acids. The content of dissolved carboxylic acid salts increases over time until reaching a threshold value.

Advantageously, this intermittent dispatch is carried out if a parameter linked to the concentration of carboxylic acid salts in the liquid effluent 112, such as the dynamic viscosity, is greater than a determined threshold value. For example, the sending of the portion 114 or all of the liquid effluent 112 in the separation unit 1004 can be triggered if the dynamic viscosity is greater than a threshold value corresponding to 3% by weight of salts of carboxylic acids. in the effluent 112, more preferably 1% by weight of carboxylic acid salts. Preferably, the initiation of the sending of the portion 114 or all of the liquid effluent 112 in the separation unit 1004 is carried out for a concentration of carboxylic acid salts in the liquid effluent 112 of between 1% by weight and 30% by weight, preferably between 1% by weight and 10% by weight. A margin can be taken into account to determine the threshold value of viscosity. Said viscosity threshold value, with the margin, is a value selected to prevent the liquid effluent 112 from becoming difficult to operate. When the viscosity of the liquid effluent reaches the threshold viscosity value, which means that the process is still operable because of the margin over the threshold value, the portion 114 or all of the liquid effluent 112 is sent into the separation unit 1004. If the required concentration is not reached, in particular if the viscosity threshold value is not reached, in the liquid effluent 112, the flow 114 is zero and all of the effluent liquid 112 can be recycled to the first unit of vacuum vaporization 1000, in order to gradually increase the concentration of carboxylic acid salts in the liquid effluent 112.

Any means known to those skilled in the art can be used to evaluate the amount of carboxylic acid salts. For example, the measurement of the dynamic viscosity of the liquid effluent 112, such as viscometers of the vibrating type or at resonant frequency.

According to a variant of intermittent operation, a portion 114 of the liquid effluent 112 obtained in step c) is sent intermittently into the separation unit 1004, while another portion 113 is recycled into the unit 1000 in step a) of vaporization under vacuum during the same time that the portion 114 is sent to step d).

However, continuous operation is possible, in which the separation unit 1004 continuously receives a portion 114 of the liquid effluent 112. In practice, in the case of continuous operation, a predetermined flow rate is established for the portion 114 of the liquid effluent 112 to be sent to the separation unit 1004.

While step c) of solid / liquid separation aims to remove the salts of precipitated inorganic acids from the MEG flow, step d) aims to remove the salts of dissolved carboxylic acids, or certain carboxylic acids liable to form salts of carboxylic acids, of said stream 114.

To do this, several ways of operating at this step d) are possible.

In step d), the separation unit 1004 can be chosen from a second vaporization unit different from the first vaporization unit, or a liquid / liquid extraction unit or a membrane separation unit or a separation unit. separation by acidification and stripping.

Other technologies making it possible to operate the separation between the salts of carboxylic acids (or the carboxylic acids capable of producing said salts of carboxylic acids) and the MEG can be used without departing from the scope of the present invention, for example the use of ion exchange resins.

According to a preferred implementation, the separation unit 1004 is a second vacuum vaporization unit, separate from the first vacuum vaporization unit 1000. The portion 114 of the liquid effluent 112 obtained in the process is vaporized under vacuum. step c) to form a vapor enriched in MEG and depleted in carboxylic acid salts 115, and a residual liquid effluent enriched in carboxylic acid salts 116.

According to this implementation, it is possible to send an additional stream 117 into the second vaporization unit to increase the quantity of MEG recovered in the stream 115. Preferably said additional stream 117 is water: a stream is sent. of water in the second vaporization unit, which makes it possible in particular to lower the operating temperature, then promoting the vaporization of the MEG and of the water and thus the separation between the salts of carboxylic acids and the MEG. This additional stream 117 can also be water vapor or an inert gas such as nitrogen or any other compound or mixture of compounds improving the recovery of MEG. According to this implementation, step d) is preferably carried out at a temperature between 120 ° C and 155 ° C, and a pressure between 0.001 MPa and 0.05 MPa. According to this implementation, the vacuum vaporization in step d) makes it possible to completely separate the carboxylic acid salts from the MEG recovered with the stream 115.

According to another implementation, the separation unit 1004 is a liquid / liquid extraction unit, and the portion 114 of the liquid effluent 112 obtained in step c) is brought into contact with an extraction liquid. to form a liquid flow of MEG depleted in salts of carboxylic acids 115 and a residual liquid flow enriched in salts of carboxylic acids 116 comprising the majority of the extraction liquid.

According to this implementation, the liquid / liquid extraction is preferably carried out at a temperature between 50 ° C and 100 ° C and a pressure between 0.1 MPa and 0.15 MPa, preferably between 0.1 MPa and 0.12 MPa.

Any extraction liquid capable of operating under these conditions can be used. The extraction liquid is advantageously insoluble with the portion 114 of the liquid effluent 112. The solubility of the organic salts in this extraction liquid allows separation by single or multi-stage extractions.

According to yet another implementation, the separation unit 1004 is a membrane separation unit, and the portion 114 of the liquid effluent 112 obtained in step c) is brought into contact with one or more membranes, in order to forming a liquid flow of MEG depleted in salts of carboxylic acids 115 and a residual liquid flow enriched in salts of carboxylic acids 116.

According to this implementation, the membrane separation is preferably carried out at a temperature between 50 ° C and 100 ° C and a pressure between 0.1 MPa and 0.15 MPa, and preferably between 0.1 MPa and 0.12 MPa.

The membrane separation is generally carried out by means of a driving force generated by a mechanical pressure difference on either side of a membrane having a pore size capable of retaining the salts of carboxylic acids on one side of the membrane. The membranes which can be used may correspond to those currently used for the separation of organic molecules of low molecular weight, for the separation of electrolytes, of non-electrolytes, for the separation of monovalent ions from divalent ions in aqueous solution, for desalting. of water. Filtration during this membrane separation can be carried out using a membrane permeable to salts of carboxylic acids and impermeable to MEG. Alternatively, the filtration can be carried out using a membrane permeable to MEG and impermeable to salts of carboxylic acids.

According to another implementation, the separation unit 1004 is a separation unit by acidification and stripping, and the portion 114 of the liquid effluent 112 obtained in step c) is acidified, then said acidified liquid effluent is stripped. with a stripping gas, preferably nitrogen or a gas comprising hydrocarbons, and more preferably nitrogen, to produce a liquid stream of MEG depleted in carboxylic acids 115 and a residual gas stream enriched in carboxylic acids 116.

According to this implementation, the separation by acidification and stripping is preferably carried out at a temperature between 50 ° C and 100 ° C and a pressure between 0.1 MPa and 0.15 MPa, and preferably between 0.1 MPa and 0.12 MPa. This implementation leads to the stripping of a subfamily of carboxylic acids, short-chain carboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid (total number carbon atoms is less than 4).

The acidification advantageously results in a solution with a pH of less than 4, so that the organic acids of this subfamily remain in their acid form, and thus favor the vaporizable form of such a subfamily of carboxylic acids. The pH of the solution can be controlled to maintain a pH below 4.

Step e) of recovering the flow of MEG from step d) and production of the regenerated solution

In this step e), either the MEG stream depleted in carboxylic acid salts (or carboxylic acids) 115 is recycled in the first vacuum vaporization unit 1000 in step a), or said MEG stream is mixed 115 with the gaseous effluent comprising MEG and water 101 obtained from step a) (not shown in the figures), and said gaseous effluent comprising MEG and water 101 obtained from step is used. a) or said mixture to produce the regenerated MEG solution.

The choice between these two options (recycled in step a) or mixing with the effluent 101) depends on the impurity composition of the MEG 115 stream, which itself depends on the type of separation used in step d) .

Preferably, the flow of MEG depleted in carboxylic acid salts (or in carboxylic acids) 115 is recycled in the first vacuum vaporization unit 1000 in step a). In this configuration, the inorganic salts which the flow may contain in dissolved form to saturation can be removed again in step a).

The production of the regenerated MEG solution can in fact be obtained indirectly from the gaseous effluent comprising MEG and water 101 from step a) or from said mixture, or by implementing step f ) of purification as described below (as shown in Figures 1 and 2), or by implementing step f) of purification and a step of vaporization at atmospheric pressure of the rich MEG solution to be regenerated beforehand in step a) also described below in the part relating to step f).

The production of the regenerated MEG solution can also be obtained directly (not shown in the figures) from the gaseous effluent comprising MEG and water 101 obtained from step a) or from said mixture, by putting in carries out the step of vaporization at atmospheric pressure of the rich MEG solution to be regenerated prior to step a), described below in the part relating to step f).

The regenerated MEG solution preferably comprises between 70% by weight and 95% by weight of MEG, or even between 70% by weight and 90% by weight of MEG.

This regenerated MEG solution does not contain salts or possibly residual salts in a content compatible with the specifications required for its reuse as a hydrate inhibitor, typically less than 100 ppm by weight.

This solution can then be used again as an inhibitor of hydrate formation, for the production and transport of natural gas, for example. Stage f) of purification of the gaseous effluent resulting from stage a) - optional

This step f) is optional.

The method according to the invention preferably operates with this step f).

The method can thus further comprise a step f) of purification of the gaseous effluent 101 resulting from step a) in a purification unit 1001 to form a stream of water 103 and the regenerated solution of MEG 102, comprising preferably from 70% to 95% by weight of MEG. This regenerated MEG solution meets the specifications required for its reuse as a hydrate inhibitor.

The water flow 103 can be collected in a reflux flask, where a water / hydrocarbon separation can be carried out if necessary.

Preferably, the purification step f) is vacuum distillation in a vacuum distillation column, advantageously carried out at a pressure below 0.1 MPa, and preferably between 0.01 MPa and 0.07 MPa.

According to one embodiment, the purification unit 1001 can receive, instead of the gaseous effluent 101 alone, a mixture of the MEG stream 115 originating from the separation step d) with the gaseous effluent 101 originating from the step a) if the composition of the stream 115 allows such mixing, in order to produce the regenerated MEG solution 102.

According to one embodiment, when step f) is not carried out, a step of vaporization at substantially atmospheric pressure of the rich MEG solution to be regenerated prior to step a) is carried out in an initial vaporization unit , preferably at a temperature between 100 ° C and 140 ° C and a pressure between 0.1 MPa and 0.15 MPa, preferably between 0.1 MPa and 0.12 MPa, to produce a gaseous effluent enriched in water and a liquid residue enriched in MEG and in salts, all of which is sent to step a).

According to one embodiment, the method comprises both said step of vaporization at substantially atmospheric pressure of the rich MEG solution to be regenerated prior to step a), and step f) of purification of the gaseous effluent obtained. of step a).

According to a preferred implementation of the invention, the process comprises the following steps: a) the solution 100 is vaporized under vacuum in the first vacuum vaporization unit 1000 to produce the gaseous effluent comprising MEG and water 101, and the liquid residue enriched in MEG and in salts 104, a first part 106 of which is recycled into the first vacuum vaporization unit 1000; b) a second part 105 of said liquid residue enriched with MEG and salts 104 is sent into the tank 1002 in which the temperature of said second part 105 is lowered so as to precipitate inorganic salts to form the stream enriched with precipitated salts 108 of which a first fraction 109 is preferably recycled into the reservoir 1002 and the flow depleted in precipitated salts 107 recycled into the vacuum vaporization unit 1000 in step a); c) is sent, preferably intermittently, a second fraction 110 of said stream enriched in precipitated salts 108 obtained in step b) in the solid / liquid separation zone 1003, comprising preferably a centrifuge, to separate the stream containing precipitated salts comprising inorganic salts 111 and the liquid effluent comprising dissolved salts among which salts of carboxylic acids 112; d) all of said liquid effluent 112 obtained in step c) is intermittently sent to a second vaporization unit 1004, different from the first vaporization unit 1000, said second vaporization unit 1004 preferably being operated at a temperature between 120 ° C and 155 ° C, and a pressure between 0.01 MPa and 0.07 MPa, and said liquid effluent 112 is vaporized to form a vapor enriched in MEG and depleted in carboxylic acid salts 115 and a residual liquid effluent enriched in salts of carboxylic acids 116; e) said vapor enriched in MEG and depleted in carboxylic acid salts 115 is recycled in step a), and said gaseous effluent comprising MEG and water 101 obtained from step a) is used to produce the regenerated MEG solution.

According to this preferred implementation, a purification step f) is carried out in a unit 1001 for purifying the gaseous effluent comprising MEG and water 101, to form a stream of water vapor 103 and the regenerated solution. of MEG 102, preferably comprising from 70% to 95% by weight of MEG, said purification step being vacuum distillation, preferably carried out at a pressure of between 0.01 MPa and 0.07 MPa. The process according to the invention, by the sequence of the steps described, thus advantageously makes it possible to recover a maximum of MEG during the regeneration of the rich MEG solution, while eliminating the inorganic salts and at least in part the salts of carboxylic acids present in the solution.

Claims

1. Process for regenerating a solution of monoethylene glycol (MEG) containing water and dissolved salts, comprising the following steps: a) said solution (100) is vaporized under vacuum in a first vaporization unit (1000) to produce a gaseous effluent comprising MEG and water (101), and a liquid residue enriched in MEG and salts (104), a first part of which (106) is recycled to said first vacuum vaporization unit (1000) ; b) optionally, a second part (105) of said liquid residue enriched in MEG and salts is sent into a reservoir (1002) in which the temperature of said second part (105) of said liquid residue enriched in salts is lowered so as to precipitate inorganic salts to form a stream enriched in precipitated salts (108), a first fraction (109) of which is preferably recycled into the reservoir (1002) and a stream depleted in precipitated salts (107) recycled in the vacuum vaporization unit ( 1000) in step a); c) is sent, preferably intermittently, said second part (105) of said liquid residue enriched in MEG and salts (104) from step a) or a second fraction (110) of said stream enriched in precipitated salts ( 108) obtained in step b), in a solid / liquid separation zone (1003) to separate a stream containing precipitated salts comprising inorganic salts (111) and a liquid effluent comprising dissolved salts among which salts of carboxylic acids (112); d) is sent, preferably intermittently, a portion (114) or all of said liquid effluent (112) obtained in step c) in a separation unit (1004) different from the first vacuum vaporization unit ( 1000) to operate a separation between the MEG and at least in part the salts of carboxylic acids or carboxylic acids capable of producing said salts of carboxylic acids and to form a flow of MEG depleted in salts of carboxylic acids in carboxylic acids ( 115) and a residual stream enriched in carboxylic acid salts or carboxylic acids (116); e) said flow of MEG depleted in salts of carboxylic acids or in carboxylic acids (115) is recycled in step a), or said flow of MEG depleted in salts of carboxylic acids or in carboxylic acids (115) is mixed. with the gaseous effluent comprising MEG and water (101) from step a), and said gaseous effluent comprising MEG and water (101) from step a) or said gas is used mixture to produce the regenerated MEG solution.

2. The method of claim 1, wherein in step e) the flow of MEG depleted in carboxylic acid salts or in carboxylic acids (115) resulting from step d) is recycled to step a).

3. The method of claim 2, wherein a further step f) of purification of the gaseous effluent (101) from step a) is carried out in a purification unit (1001) to form a water flow. (103) and the regenerated MEG solution (102), preferably comprising from 70% to 95% by weight of MEG.

4. The method of claim 3, wherein the purification step f) is vacuum distillation, preferably carried out at a pressure between 0.01 MPa and 0.07 MPa.

5. Method according to any one of the preceding claims, wherein, prior to step a), vaporization is carried out at atmospheric pressure of the MEG solution containing water and dissolved salts (100) to be regenerated in an initial vaporization unit, preferably at a temperature between 100 ° C and 155 ° C and a pressure between 0.1 MPa and 0.15 MPa, to produce a gaseous effluent enriched in water and a liquid residue enriched in MEG and salts, all of which are sent to step a).

6. Method according to any one of the preceding claims, wherein step a) is carried out at a temperature between 120 ° C and 155 ° C, and a pressure between 0.01 MPa and 0.07 MPa.

7. Method according to any one of the preceding claims, wherein step c) is carried out at a temperature between 50 ° C and 90 ° C and at atmospheric pressure, preferably at a pressure between 0.1 MPa and 0.15 MPa.

8. Method according to any one of the preceding claims, wherein the second fraction (110) of said stream enriched in precipitated salts (108) from the reservoir (1002) is sent into the solid / liquid separation unit (1003) of intermittently, preferably if the concentration of inorganic salts of said stream enriched in precipitated salts (108) is between 10% by weight and 50% by weight, preferably between 15% by weight and 30% by weight.

9. Method according to one of the preceding claims, wherein the portion (114) or all of said liquid effluent (112) obtained in step c) is sent intermittently into the separation unit (1004) of the step d).

10. Method according to one of the preceding claims, wherein in step d) the separation unit (1004) is chosen from a second vaporization unit or a liquid / liquid extraction unit or a separation unit by membrane or a separation unit by acidification and stripping.

11. Method according to any one of the preceding claims, wherein in step d) the separation unit (1004) is a second vaporization unit, and the portion (114) or all of said effluent is vaporized under vacuum. liquid (112) obtained in step c) to form a vapor enriched in MEG and depleted in carboxylic acid salts (115) and a residual liquid effluent enriched in carboxylic acid salts (116).

12. The method of claim 11, wherein an additional liquid or gaseous stream (117) is sent into said second vaporization unit to increase the quantity of MEG recovered in the stream (115) during step d), said stream. being chosen from water, water vapor, or an inert gas.

13. Method according to any one of claims 11 and 12, wherein step d) is carried out at a temperature between 120 ° C and 155 ° C, and a pressure between 0.01 MPa and 0.07 MPa. .

14. A method according to any one of claims 1 to 10, wherein in step d) the separation unit is a liquid / liquid extraction unit, and the portion (114) of said liquid effluent is brought into contact. (112) obtained in step c) with an extraction liquid, preferably at a temperature between 50 ° C and 100 ° C and a pressure between 0.1 MPa and 0.15 MPa, to form a flow MEG liquid depleted in carboxylic acid salts (115) and a residual liquid stream enriched in carboxylic acid salts (116) comprising the majority of the extraction liquid. 15. A method according to any one of claims 1 to 10, wherein in step d) the separation unit is a membrane separation unit, and the portion (114) of said liquid effluent (112 is brought into contact). ) obtained in step c) with one or more membranes, preferably at a temperature between 50 ° C and 100 ° C and a pressure between 0.1 MPa and 0,

15 MPa, to form a liquid flow of MEG depleted in salts of carboxylic acids (115) and a residual liquid flow enriched in salts of carboxylic acids (116).

16. A method according to any one of claims 1 to 10, wherein in step d) the separation unit is a separation unit by acidification and stripping, and the portion (114) of said liquid effluent (112) is acidified. ) obtained in step c) then said acidified liquid effluent is stripped with a stripping gas, preferably nitrogen, preferably at a temperature between 50 ° C and 100 ° C and a pressure between 0.1 MPa and 0.15 MPa, to form a liquid flow of MEG depleted in carboxylic acids (115) and a gaseous residual flow enriched in carboxylic acids (116).